This proposal has as its main objective to study leprosy in the armadillo with particular emphasis on determining the most susceptible individuals of the species. The genetically-identical littermates of these animals will be used as breeders to develop an armadillo strain that will develop leprosy rapidly and with predictable uniformity. A second phase of this proposal is to study the susceptibility of newborn armadillos to leprosy. A third phase is to study lepromin reactivity in these animals and also to study the serum proteins of normal and infected animals.